Fuel pump



2, 1958 A. c. RIDLAND 2,846,952

FUEL PUMP Filed Dec. 27, 1955 1045 hip/V052 C. Q/OLi/VD INVENTOR.

United States Patent FUEL PUMP Alexander C. Ridland, Rancho Santa Fe, Califl, assignor to Hydro-Aire, Inc., Burbank, Calif., a corporation of California Application December 27, 1955, Serial No. 555,444

3 Claims. (Cl. 103'113) This invention relates to liquid fuel pumps and more particularly to a unitary pump unit for aircraft or other applications wherein vapor conditions in the pump can cause flow failures.

Great difliculties have been experienced in pump applications handling liquids at pressures approximating the vapor pressure of the pumped fluid. It is a rather common occurrence in aircraft fuel systems due to extremely wide range of temperature and pressure conditions encountered. The problem is especially acute following resumption of fuel demand after a period of either no flow or reduced flow conditions at high altitude. There are a number of reasons for this. For example, the pump impeller may become submerged in vapor derived from the fuel tank, or generated by heat from the driving motor, or merely from the action of the rotating impeller in liquid at a pressure close to its vapor pressure, or a combination of these and other factors. This condition isolates the impeller from liquid and prevents it from exerting a propelling force thereon until the vapor can be condensed or expunged from the pump in some manner. Even a moments delay in rectifying the condition can be fatal if it occurs when the pilot expects and requires full and instantaneous resumption of fuel flow to meet an emergency situation.

The present invention has been found to provide a simple yet fully reliable means of safeguarding against flow failure due to the presence of vapor or gas in the pump impeller chamber. This is done by the simple expedient of maintaining a minimum flow of liquid through the pump inlet and past the entrance end of the pump impeller at all times including periods when the discharge outlet proper is throttled or even closed. This continuous circulation of fuel through a short circuit in parallel with the main fluid circuit not only serves to maintain the impeller below vapor generating temperatures but keeps the pump inlet purged of vapor so that the impeller blades are always in contact with liquid and exerting-a propelling force thereon.

Accordingly, it is an object of the invention to provide apumpdesign which is not subject to flow failure due to vapor lock under any operating conditions in which liquid can reach the pump inlet.

Another object is the provision of a simple, rugged fuel pump having means for circulating a predetermined amount of fuel past the fluid propelling element even when little orno fuel flow is permitted from the pump outlet.

Yet another object is the provision of a power-driven pump unit designed for use while submerged and having special provision for safeguarding the same against failure due to gas or vapor pocket-s within the pumping chamber.

These and numerous other objects and advantages will become readily apparent from the following detailed specification of an illustrative embodiment taken in connection with the accompanying drawings, wherein:

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Figure 1 is a vertical sectional view taken upon the line 1-1 of Figure 2 showing my pump assembly extending upwardly into a fuel tank from its bottom wall; and

Figure 2 is a fragmentary sectional view along line 22 of Figure 1 showing the disposition of my vapor purge ports opening through the wall of the pump inlet adapter.

Referring to the drawings it will be seen that my pump assembly includes a generally tubular main housing 10 enclosing an electric driving motor of any suitable sealed type for submerged operation and directly coupled to a liquid fuel pump generally designated 12 disposed at the opposite lower end thereof. It will of course be appreciated that an air turbine, a hydraulic motor or any other known means of converting transferable'energ'y to mechanical motion may be used in lieu of the electric motor if so desired.

The lower end of motor shaft 14 extends through a fluid seal 27 housed within a cavity 23 of the cupped partition 24 held assembled to the top of the pump body by screws 22. An O-ring 26 is seated in an annular groove in ring 24 to form a fluid seal with the motor casing. The mechanical fluid seal 27 provides a fluid seal between the motor chamber and pump chamber at the rotating shaft 14.

As here shown, the pump impeller has a generally conical hub fastened to the lower end of shaft 14. Spirally encircling its exterior is a continuous convoluted impeller blade 29 projecting perpendicularly from the surface of hub 28 and extending substantially from the tip to the base end in the manner illustrated in Figure 1. Its outer free edges terminate in closely spaced relation to the conical inner surface 30 of the inlet adapter 31. This adapter has an outwardlyflanged rounded inlet 32 suitably spaced above the combination cover and mounting plate 33 for the unit. The

periphery 34 of the plate 33 projects appreciably beyond,

outer side walls of casing 10 to provide a mounting flange adapted to seat against the edges of an inlet opening 35.

cut in the bottom wall 36 of fuel tank 37-. 7 Pump inlet adapter 31 is provided with a peripheral flange 38 which may be secured to the lower end of housing 10 ,by screws 39. Housing 10 has a number of supporting legs 40 spaced apart so'as to provide large area fuel inlet openings 41 about the base of the unit. These openings. are preferably guarded by ascreen or grille work 42..

The means for preventing convoluted pump chamber 43 from becoming clogged with quiescent gas or vapor preferably comprises a series of small diameterports 44 extending through wall 31 of the inlet adapter at a point generally opposite the lowest convolution of impeller blades 29. Most eifective results are obtained by locating the axes of these ports generally tangential to the interior face 30 of the inlet adapter. In consequence, the gas and liquidbeing contacted and propelled by the lowest convolution of the impeller 28 is highly effective in returning a certain quantity of the fluid being pumped back into the tank or supply source through bypass ports 44.

During normal operation of the pump, the main body of the fluid contacted by the impeller is propelled into the volute-shaped pump discharge chamber 45 which opens through the side wall of housing 10 at a point di- The operation of my pump will be quite obvious from the foregoing description. Under normal operating eonably submerged enters through the grille 42 and passes upwardly through inlet 32. The impeller blades 29 driven by;mo.t;or.- 11-..propel-1 themajon-portion-of; the fuel enter- HS-;,i let:32-upwardly anduoutwardlyrinto the discharge convolute.;45..- However,-a relatively smalls-percentage. is discharged outwardly through purge openings 44'." Any vaportpresent. in thepurged fuelwwill rise upwardly about the-sidesi-iofrthe. pump; housing -whereas liquid portions willlrecirculatewbaelc into the: pump inlet. Thecapacity of the bypass ports is so designed that the fuel so purged does notinterfere with the -maximum-.fuel"requirements of..the system supplied: by. the. pump.-

Let: it be assumed that the-fuel-- demandceasesand that the. utlet:-.to:.-chamber .45 is closed or substantially so Let: 1153150136,. assumed that the-fuel surrounding the pump.v is close tosthe-vaporpressurer Under these conditions....the..ro.tation.of thepump impeller together with the. heatgenerated by the motor will cause considerable fuel., -to. bervaporized and to' collect inthe pump inlet adapter. Eventually the entire chamber would become filled...with the..vapor were itnot for the action of the lower convolution -of, the impeller .in circul'ating fuelthtoughbypass ports.44. Buteven. though the entire upper.. por.tionof the .pump, chamber becomes filled Withyapor the lower end will beflooded with liquid circulatingthrough the bypassports. This circulation will not. only maintain the lower endv of the pump and its inlet free of vapor, but it will keep 'a stream of liquid flowingpast the impeller 28 to cool the same. This coolingeffejct'. plus the. increased pressure caused by the impeller may even result in. the condensation-of. the vapor collected. in the..upper portion of the pump chamber.

In' con'sequence. of the foregoing and upon the reopeningof. the, fuel valve, even though this opening be to a limited extent,,.the .lowerturn ,of the impeller, submerged as .it always is in .liqu idgwill be immediately effective in propelling fuelupwardly topurge the upper portion of the chamber of vap,or,as.well as :to circulate fuel tothe point of use. Hence, .the pump is eifective to resume fuel flow vatany rate desired in a negligible period of time.

Fromthe foregoing. itwillflbe' readily apparent that the present inventionprovides "aniunusually simple yet.

highly effectiveconstruction for assuring fuel flow under the -most extreme and .exactingoperating requirements and despite conditions tending to create vapor lock conditions within the pump chamber.. The design is not only capable of positively purging. .thepump. of any vapor pockets but it operates in'a manner greatly discouraging the conditions conducive to their formation.

Having now described my inventionandin what manner'the'same may be used,what I claimis new and desire to protect by Letters Patent is:

I claim: I

1. *A submerged fuel pump adapted for mountingv in aliquid fuel-tankcomprising, a casing defining .an..upwardly -and'outwardly flaring volute andincluding an inlet-adapter,- said adapter having. an axial inlet at its lower end'in lateral communicationwith liquid fuel surrounding-said pump and 'a peripheral outlet atits .upper end'for connection'with a point of liquid fuel-delivery, apower-driven outwardlyflaring conical impeller rotatably-supportedinsaid inlet adapter having spirally'arranged blade means thereon for .propelling fuel through said inletand'dischargingthe same from said outlet, and.

aplurality *of fuel outlet ports opening outwardly through the side wall-of said inlet adapter radially opposite said impeller-blade means atpoints closely adjacent said fuel inlet-whereby -vapor present in theiinlet area of said pump is discharged through said fuel ports so that liquid fuel. can contact said *blademeans' and be propelled thereby toward said fuel outlet."

2. A submerged fuel; pump. as .defin'edin claim -1 wherein said fuel ioutletlports havetheir. axesdisposed" generally tangentially .to the side Wall of said inlet adapter whereby said spirally arranged impeller blade means 0perate with maximum efliciency in purging the volute chamber of vapor.

3. A submerged fuel pump as defined in claim 1 wherein the portion of said inlet adapter enclosing said impeller is of frustoconical configuration with said fuel inlet at the small diameterend thereof, said impeller having a conical hub provided with thin spirally arranged blade means projectingrsubstantially normal to the surface of said hub from the tip toward the base end thereof, and said fuel outlet ports being located close to but spaced inwardly from the inletend of said impeller.

4. A submerged fuel pump as defined in claim 1 wherein said pump includes a base plate connected thereto but lying in a transverse plane spaced below the inlet to said inlet adapter and adapted to support said pump inwardly of but close to the bottom wall of a fueL'tank.

5. In combination, a compact fuel pump assembly adapted for use while submerged in fuel and capableof producing substantially instantaneous fuel'flows even after"- extended periods of operation with flow from the delivery outletsubstantially. shut off, said pump assembly includ-- ing; a tubular housing'h'av-ing an electric motor sealed within itsupper end and a frustoconically-shaped inlet adapter formed in its opposite end, an impeller housed in said inlet'adapterhaving a conical hub supporting spirally pocket of fuel vapor in said inlet adapter, said cavitationprevention-means.including fuel outlet ports opening outwardly through the inlet adapter. side wall on a plane transversing the inlet adapter'near'the small diameter end thereof whereby said impellercontinues to circulate the. fuel outwardly through said ports even .during zero: flow conditions in the pump circuit proper and serving tomaintain said impeller cool and to bleed vapor from the inlet adapter.

6. A fuel :pumpfor use infuel supply lines ofaircraft.

subject to widely fluctuatingtemperatureand pressure conditions likely to cause the presence of substantial percentagesof fuel vapor inthe streams being handled by the pump, said pump havinga casing forming an inlet 1 adapter with a downwardly-opening central fuelinlet and a peripherally disposed outlet thereabove, said inlet tinuous flow of fuel. through the inlet of said pump even during periodsin which said outlet is blocked forithe purpose of cooling said impeller and safeguarding against 2 the same becoming submerged in fuel vapor, said means;-

comprisinga series oftangential 'vaporoutlet openings of restricted capacity leading back into: thefuel supply throughthe wall of said inlet iad-apter'at a level spaced between the inlet and outlet thereof, the combined capacity of said tangential vapor outlet openings being appreciably lessthan the1mainfueloutlet at the upper-end of said pump chamber.

7. A fuel pump as defined in claim 6 including means" for supporting said pump interiorly of a fuel tank from the bottom wall thereof with the pump inlet lying in a plane substantially coincident-with the-bottom of the tank.

8. A fuel pump as defined in claim 6 wherein the inner" ends of said restricted capacityfuel openings are directly opposite and swept by the blade means at the lower end of said impeller action tending to circulate fuel through said restricted openings whenever said impeller is operating, said impeller having a conical hub and the blade means carried thereby being substantially normal to the conical surface of said hub and effective in throwing entrained fuel vapor outwardly for escape through said restricted openings back into the fuel tank.

References Cited in the file of this patent UNITED STATES PATENTS Tait Aug. 28, Stepanofl? Nov. 13, Edwards May 8, Adams I an. 8, Di Stefano et 'al. Sept. 4, 

